A casement window has a window sash which is moveably mounted within a frame by a pair of hinges mounted between the window frame the top and bottom of the window sash. Normally, the arrangement is such that one has a track mountable to the window frame and a sash arm connectable to the window sash. A support arm interconnects the track and the sash window with the support arm being pivotably connected to the sash arm and to the track. The sash arm is pivotably connected to a mounting shoe which is supported and guided for movement lengthwise of the track.
It is also known to provide an intervening link between the sash arm and the moveable shoe to provide for an offset sash arm. Such an arrangement typically includes a second intervening link between the support arm and the moveable shoe to provide further support.
Casement window operators are well known and typically include a hand crank which drives a worm gear arrangement which is connected to an arm or lever which pushes the window sash open. The worm gear assembly includes a gear shaft having the worm at one end thereof with the other end of the gear shaft extending outwardly through the housing to engage a crank. When the crank is turned, the worm causes the worm wheel to rotate and which in turn causes the sash to pivot on its hinges between open and closed positions.
As aforementioned, there are different opening arrangements for casement windows. A first type is a single arm operator which has an arm which pivots about an axis that is fixed with respect to the window frame and worm gear. The remote end of the arm carries a bearing which slides in a track mounted to the underside of the sash. A disadvantage with single arm operators is the torque required to move the sash towards its fully open position.
A second type of casement operator is the split arm variety. A split arm operator includes a second arm which has a pivot point in the middle of the second arm and the remote end of the second arm is secured through a pivotable mounting to a fixed point on the sash. While a split arm operator allows the window to extend to its fully open position, it does present difficulty at the time of the initial opening of the sash.
A third type of window operator is a dual arm operator which has one arm which rotates about a fixed axis and a housing which carries at its far end a bearing to slide in the track mounted to the window sash. There is also a second arm which has a pivot joint and which is secured at its remote end by a pivotable but fixed connection to the sash.
Many of the operators described above are relatively complex and difficult to assemble such that they will function in a reliable manner. A further problem in northern climates is the tendency of the operator to permit infiltration of cold air thus driving up energy costs.